1. Field of the Invention
This invention generally relates to wireless networks and to IP Multimedia Subsystem (IMS) networks.
2. Description of Related Art
Multimedia sessions are typically carried by a packet-switched wireless network, such as the IP Multimedia Subsystem (IMS). The IMS architecture manages the network with several control functions, i.e., functional entities. FIG. 1 is a schematic illustration of select functional entities typical of conventional IMS networks and their interaction with a user's handset. The IMS network includes a control plane 100, which is partitioned into a switching layer 110 and a service layer 120. The switching layer 110 is controlled by a logical function called the Call State Control Function (CSCF), which is logically partitioned into three functional entities: the Proxy, Interrogating and Serving CSCFs. The Proxy Call State Control Function (P-CSCF) 104 is the first contact point for a user's handset 102, also referred to herein as the User Entity (UE). The Interrogating CSCF (I-CSCF) 106 is mainly the contact point within an operator's network for all IMS connections destined to a subscriber of that network operator, or a roaming subscriber currently located within that network operator's service area. The Serving CSCF (S-CSCF) 108 actually handles the session states in the network. The S-CSCF 108 interacts with the service layer 120 to provide services to the UE 102. More specifically, application servers (ASs) 122, 124, 126, which may be third party or part of the home network, provide services to the UE, such as voice mail, via the S-CSCF 108. The IMS controls packet services among the different functional entities with signaling protocols such as Session Initiation Protocol (SIP), which is an IP-based signaling protocol designed for multimedia communications.
When UE 102 first powers on, logic residing in the UE initiates a REGISTER procedure with the IMS core, first by requesting the mobile wireless access network (not shown) to assign it an IP address. After it receives an IP address, the UE 102 attempts to register as an IP-enabled endpoint with the IMS core by sending a REGISTER request to the P-CSCF 104. Assuming that the UE 102 is registering from a visiting domain, the P-CSCF 104 then uses a Domain Name Server (DNS) to search for the UE's home domain S-CSCF 108. Once the P-CSCF 104 locates the S-CSCF 108 for the UE, it passes the REGISTER request to that S-CSCF 108. The S-CSCF 108 contacts the Home Subscriber Subsystem (HSS) 112, which looks up the UE's profile. This profile contains information about the UE 102, and what services the UE is authorized to use. A logical function in the S-CSCF 108 called the registrar then authenticates the UE 102, e.g., verifies that the UE is legitimate.
In a conventional IMS network, the HSS 112 also provides a list of Initial Filter Criteria (iFC) to the S-CSCF 108 via the UE's service profile during UE 102 registration. The S-CSCF 108 stores the iFC while the UE 102 is powered on. The iFC maps service requests onto the various application servers, and thus is effectively the call model for the UE 102. When the S-CSCF 108 receives a service request from either the UE 102 or from another entity, it triggers a Service Point Trigger (SPT) based on the iFC and the information contained within the service request. This information conventionally includes the calling party's Universal Resource Identifier (URI) and the Service Description Protocol (SDP), which describe any multimedia service requested, e.g., picture or video. The matching SPT defined in the iFC, in turn, invokes the appropriate Application Server (AS), e.g., AS 122, 124, or 126. For example, if the UE 102 requests voice mail service, the SPT triggers the S-CSCF 108 to forward the service request to the voice mail AS, e.g., AS 122.
If an entity wishes to engage in a transaction with the UE 102, e.g., to send a message to the UE, the entity utilizes an AS, e.g., AS 124, to send a request for the transaction to the S-CSCF 108. This may trigger an SPT in the S-CSCF 108 based on the iFC, and the S-CSCF in this case would forward the request to another AS. If there is no SPT triggered in S-CSCF for SIP requests received from this particular AS, the S-CSCF will route the SIP requests toward the destination. Other ASs may not know which S-CSCF 108 to contact in order to engage in a transaction with a particular UE 102. In this case, the AS interrogates a Subscriber Location Function (SLF) (not shown), which provides information about the UE's S-CSCF 108 to the AS, which then contacts that S-CSCF as described above. If the UE 102 wishes to request a service, it sends the request to the S-CSCF 108 using a SIP Invite message. This triggers an SPT in the S-CSCF based on the iFC, and the S-CSCF 108 then directs the service request to a particular AS which then provides the service to the UE 102. For example, if the user wants to initiate an IMS call, the UE 102 sends a SIP Invite message to the S-CSCF 108, e.g.,which may then contact the AS responsible for IMS calls, e.g., AS 126.
A conventional IMS call model, based on iFCs, is a linear, static service provisioning and invocation model. Every UE subscriber with the same service subscription, within the same home service domain, is provisioned with an identical iFC which invokes the same or equivalent AS, e.g., AS 124, when the same service request is received. For example, video streaming service for each and every UE having such a service, in the domain of the S-CSCF 108, will point to the same AS or to an AS with service logic capable of providing the same video streaming service.
This limitation extends to Mobile Virtual Network Operators (MVNOs), which are entities that purchase a network provider's services wholesale, and then resell those services to their subscribers. MVNOs, through a business agreement, effectively use the network operator's facilities without owning the network infrastructure or spectrum license. Thus, wireless services can be offered by several MVNOs (as virtual service providers) using the same underlying network infrastructure. One problem with such an arrangement is that service differentiation is not possible among various MVNOs using a common network operator since these MVNOs are tied to the same network infrastructure, including the service logic. Thus, if two MVNOs, MVNO1 and MVNO2, both use the same network operator and both provide voice service, that service typically will be indistinguishable to end users of the voice service regardless of whether they use MVNO1 or MVNO2. Thus, MVNOs conventionally distinguish their services mainly through marketing, handsets, and billing.
FIG. 2 is a schematic of a conventional IMS service profile 200 for all UEs in the domain of a conventional S-CSCF 108. The domain includes UEs subscribing to a given network operator, as well as any UEs that may subscribe to MVNOs that use that network operator's equipment and license. The single service profile, i.e., one set of policies, governs all of the ASs, e.g., AS 122, 124, 126, that provide services in that domain. The conventional IMS service profile 200 includes a specification of standard services 210 associated with the service profile, including authentication, accounting, and addressing (AAA) services. The service profile 200 also includes iFCs for various services that are authorized in the domain, for example, Instant Messaging (IM) 220 and Presence 230. The iFCs 220, 230 include SPTs that invoke an appropriate AS in response to a service request. Thus, when any UE within the domain requests, for example, the Instant Messaging service, the request invokes the Instant Messaging AS.
For further details on conventional call models, iFCs, SIP, SDP, Mobile Independent Handoff (MIH), IMS signaling protocols, and IMS networks in general, see, for example, the following technical specifications, the entire contents of which are incorporated herein by reference: 3GPP TS 23.228 V6.8.0 (2004-12); 3GPP TS 23.218 V6.3.0 (2005-03); 3GPP TS 24.228 V5.12.0 (2005-03); and 3GPP TS 24.229 V6.6.0 (2005-03).